1. Field of the Invention
The present invention relates to a semiconductor integrated circuit design support system, a design support method for a semiconductor integrated circuit, and a semiconductor integrated circuit and, more particularly, to a semiconductor integrated circuit design support system, a design support method for a semiconductor integrated circuit, and a semiconductor integrated circuit for performing partial power control by software.
2. Description of Related Art
Demand for less power consumption of semiconductor integrated circuits has recently increased. For the reason, a partial power-off technique for powering off an unused circuit section in a semiconductor integrated circuit while the circuit section is not used has been widely adopted in semiconductor integrated circuits.
Since the number of circuit sections, i.e., circuit ranges (hereinafter referred to as power domains) to be powered off and the number of combinations of power domains to be powered off were small in the past, a power control section was designed to be realized by a logic circuit, verified, and implemented in a semiconductor integrated circuit.
However, implementation by a logic circuit suffers from a problem of an inability to respond to different demands for low power consumption, due to an increase in a scale of semiconductor integrated circuits and diversification of demands for low power consumption in recent years. A software power control system in which power control is performed by software using an embedded microprocessor is being introduced for power control instead of a system using a logic circuit, as disclosed in, e.g., U.S. Patent No. 2008/0127015A1 or Hiroshi Nakamura, “Innovative Power Control for Ultra Low-Power and High-Performance System LSIs,” Japan Science and Technology Agency, September 2008, retrieved from the Internet on May 18, 2009.
Even in the case of a power control system using software, the number of power modes for power control (i.e., the number of combinations of on/off statuses of a plurality of power domains) may be enormous. As for the number of power modes, since there are combinations, the number of which is 2 to the power of the number of power domains. For example, if the number of power domains is 20, the number of combinations is 1,048,576. For the reason, it is physically extremely difficult to thoroughly verify operation of a semiconductor integrated circuit for each of all combinations.
However, verification of a power mode in a semiconductor integrated circuit only within a range originally required by a user causes the following problem. If a power mode actually used in the semiconductor integrated circuit is changed, and a power mode outside the originally required range is run, since the power mode falls outside the originally required range and has not been verified, a malfunction may occur in the semiconductor integrated circuit.
That is, if there is inconsistency between an originally intended power mode and an actual power mode, a problem such as a malfunction in a semiconductor integrated circuit may occur due to insufficient verification.